docs: def _readStreamHeader(self):
          """
          Reads the magic header of a Java serialization stream
  
          :raise IOError: Invalid magic header (not a Java stream)
          """
          (magic, version) = self._readStruct(">HH")
          if magic != self.STREAM_MAGIC or version != self.STREAM_VERSION:
              raise IOError(
                  "The stream is not java serialized object. "
                  "Invalid stream header: {0:04X}{1:04X}".format(magic, version)
              )